PdII and PtII Metal-Directed Self-Assembly of Supramolecular Structures Based on N-Monoalkyl-4,4¢-Bipyridinium Derivatives - Molecular Self-Assembly: Advances and Applications - page 352

11.1 Introduction

Supramolecular chemistry has been traditionally defined as
“ chemistry beyond the molecule ,” “ the chemistry of the noncovalent

bond ” or “ chemistry of molecular assemblies and of the intermolecular

bond [1]. In any case, the definition of supramolecular chemistry

must mention (implicitly or explicitly) noncovalent interactions
such as hydrogen bonding, ion-ion, ion-dipole, dipole-dipole,
and van der Waals forces, which are intrinsically associated with
the formation of any supramolecular structure. Although a young
scientific field, the last decades have witnessed the impressive
advances on the development and understanding of host-guest
chemistry and self-assembly processes. These two topics are very
closely related to the birth and growth of supramolecular chemistry
itself. Host-guest chemistry is concerned with the recognition
processes between, at least, two molecules. Therefore, a substrate
or guest is recognized by a receptor or host, the former been
defined as the smaller component on the aforementioned complex.
Supramolecular self-assembly implies the self-organization of
several simple components toward the formation of complex well-
defined architectures. Thus, self-assembly has been defined as “

”

the
spontaneous and reversible association of molecules or ions to form
larger, more complex supramolecular entities according to the intrinsic
information contained in the molecules themselves ” [2].

11.2 Self-Assembly Strategies

Metal-coordination-directed self-assembly of well-defined
supramolecular structures is a growing area at the forefront of
supramolecular chemistry [3-9]. In addition to their remarkable
formation reactions, based on self-assembly processes and the
unusual structures created, metallocyclophanes have attracted
attention owing to their potential for use as sensors, probes,
photonic devices, catalysts, and in basic host-guest chemistry
[10-12]. In this context, metallocycles such as molecular triangles,
squares, pentagons, and hexagons have been synthesized in the last
few years. Although they can be considered as potential receptors
for aromatic systems, quadrangular molecular structures have
remained relatively rare.